From plastic armored hulls to turbines: a quarter in the life of Soviet tank builders
Experience son of difficult mistakes
The archives of the Soviet military-industrial complex are gradually becoming accessible to a wider audience. Many collections hold invaluable archives, but the most comprehensive is considered to be the Russian State Archive of Economics, whose materials have been published in the pages of "Military Review" several times. This time, it's the turn of a once-top-secret explanatory note to the report of the Moscow branch of VNII-100 (now the All-Russian Scientific Research Institute of Transport Engineering) for the third quarter of 3. The document provides a snapshot of the institute's specialists' work on issues related to domestic tank development. Of interest are not only the initial developments in aluminum and titanium armor but also attempts to create plastic armored hulls. It also reveals the organizational aspects of the research staff's work at this leading institute in the armored vehicle industry. For reference: until 1961, the Moscow branch of VNII-100 was known as the All-Union Scientific Research Institute of Steel. The document is published with minor edits. The drawings are not directly related to the report and are intended to illustrate the profile of the work of VNII-1967 in the early 100s.
Explanatory note to the report of the VNII-100 Branch for the third quarter of 1961
In the past third quarter of 1961, the Branch, in accordance with the approved plan, carried out research work in the following areas:
- creation of combined protection tanks from all modern weapons (cumulative, armor-piercing and sub-caliber projectiles, missiles and radiation exposure);
- reducing the weight of armored vehicles by introducing lightweight aluminum and titanium alloys for both armor and structural purposes;
- development of new low-deficit and cost-effective heat-resistant alloys that provide increased power and forced modes of tank engines;
- providing technical assistance to tank industry plants in the field of mastering the production of new objects, improving technological processes, reducing defects and increasing productivity.
This explanatory note contains a brief listing of the work performed by the Institute, indicating, in some cases, the measures necessary to ensure its continued uninterrupted implementation. These works are, largely arbitrarily, divided into several groups corresponding to the main problems whose solution falls within the Branch's specialization.
Protection against penetrating radiation
Work in this area is being conducted under topic NT2-321-61. During the quarter, the penetration of the main components of radiation through various material barriers was studied. The protective properties of combined barriers (steel-lead, steel-hydrogen-containing materials, etc.) were investigated. A number of materials and their combinations were tested as promising neutron radiation shielding, including titanium hydrides, iron-filled plastics, and others. All experiments were conducted at a radiation energy of 0,66 MeV.
A methodology has been developed for calculating radiation protection measures for armored vehicle models, which is currently necessary to support the design work of the newly created infantry combat vehicle.
Preparations for further field research have begun. A portable field generator, the NG-200, has been manufactured. A dedicated plot of land has been allocated at the Research Institute 58 testing ground.
To ensure further timely and uninterrupted provision of the subject, it is necessary to carry out a series of construction and excavation works to equip the site (leveling, fencing, etc.) as quickly as possible.
Active methods of protection against cumulative projectiles
Subject TM-921-59. During the development of active anti-cumulative protection methods, two plates measuring 1,2 x 2,5 meters and 100 and 80 mm thick were designed and manufactured, equipped with anti-cumulative devices operating on the "fragment" principle. The plates have been sent for testing to military unit 68054. Production of a pilot turret sector for Object 432, capable of countering a cumulative jet using dynamic protection, is nearing completion.
Furthermore, extensive research was conducted on the ability of various materials and their combinations to passively resist the effects of 85mm to 122mm HEAT projectiles. Steel-fiberglass and aluminum-steel systems were tested on the armor of Object 432 (T-64) and Object 287 (a missile-armed turretless tank, not put into production).
Major difficulties arise as a result of systematic delays in conducting firing tests at the firing range of military unit 68054, which poses a threat to the timely fulfillment of the plan for the fourth quarter.
Development of multilayer armor protection for tanks
During the TM-671-60 and TM-719-60 projects, two variants of three-layer composite armor were developed: "titanium-aluminum-titanium" and "steel-aluminum-steel," providing protection against powerful modern subcaliber and shaped-charge projectiles of the Molot system. The first of these combinations provides approximately 40%, and the second approximately 33% weight savings compared to steel armor of equal protective properties.
Firing tests of slabs and experimental three-layer sectors were carried out.
The results of this work were used in the design, casting, and heat treatment of two experimental turrets for Object 2, constructed with three-layer armor—steel-aluminum-steel. These turrets, manufactured according to the State Committee for the Protection of the Armored Vehicles (Project NOZ-432-999), are currently being prepared for field testing.
In the TM-782-61 project, the optimal type and composition of fiberglass plates for the production of composite multilayer armor was determined. A manufacturing technology was developed jointly with the NIIPM (Institute of Plastics). Firing tests of composite armor (steel-fiberglass) allowed for the determination of the key parameters necessary for calculating and designing this type of protection for Object 432.
At the same time, a number of other metallic materials capable of providing reliable armor protection when combined with fiberglass were studied. It was shown that the use of OT4-1 titanium alloy with a fiberglass liner allows, without compromising protection, to reduce the armor weight by 25-30% compared to a steel-fiberglass system, or to significantly enhance its protective properties while maintaining the same weight. For example, the upper glacis plate of Object 422, made of OT4-1 alloy with a fiberglass liner, without increasing weight and with the same level of radiation protection, does not cause through-holes when fired at by Molot subcaliber projectiles and shaped-charge projectiles, which can penetrate up to 550 mm of medium-hard steel armor.
In the fourth quarter, research will be conducted on new variants of the steel-fiberglass system (multilayer liner, etc.) to explore possibilities for simplifying the production process. To further test the protective properties of the OT4-I alloy, production of a prototype hull made of titanium armor with a fiberglass liner is planned for the near future.
Development of aluminum armor
During the TM-719-60 project, firing tests were conducted on experimental forged armor made from AMg6 and AMg7 aluminum alloys. The tests were conducted with 122mm caliber armor-piercing rounds at impact angles of 60° and higher. The tests demonstrated that the use of this armor, without compromising its protection, can provide a 15 to 35% weight savings compared to steel.
Under the KT2-010-60 project, tests of a tank with an aluminum hull were conducted in accordance with the approved program. The tests included high-speed obstacle crossing, firing, towing, turning on a slope, and climbing a vertical wall. The tests revealed the good performance qualities of aluminum hulls. However, the tests revealed insufficient strength of several aluminum chassis components (brackets, idlers, and rocker stops). This deficiency was addressed through appropriate design modifications.
The branch developed temporary technical specifications for the manufacture of aluminum enclosures and compiled process instructions. According to these specifications, three new pilot aluminum enclosures are currently being manufactured at STZ, in accordance with a government decree, with the branch's ongoing technical assistance. The work is expected to be completed in the fourth quarter.
Research into the possibility of using bulletproof aluminum barriers to protect light tanks and armored personnel carrier hulls, carried out under the TM-744-61 project, showed that aluminum alloys with a temporary resistance of 50-60 kg/mm have optimal bulletproof resistance.2 and a hardness of 145-160 Brinell units. The use of such alloys will reduce the non-penetration range by 100 meters.
Further work in this area is focused on identifying alloys with the specified characteristics capable of producing reliable welded joints. At the same time, the existing methodology for assessing the weldability of aluminum alloys will be refined to meet the requirements of armored hull production.
Development of titanium armor
During the planned work on Project TM-744-59, several advantages of OT-4 titanium alloy armor over steel were demonstrated. Titanium armor, while offering equal resistance to steel, offers approximately 30% weight savings against armor-piercing and subcaliber projectiles from the Molot and Rapier systems. When firing shaped-charge projectiles of existing calibers, this savings increases to 35%. A technology for melting, casting, and rolling armor plates from OT-4 alloy has been developed. Significant challenges were encountered in resolving issues related to welding titanium armor, which is a priority for future work.
Laboratory experiments conducted under TM-671-60 yielded data demonstrating the feasibility of using electroslag melting to produce cast titanium armor plates with protective properties similar to those of rolled metal. Work continues on testing pilot ingots and determining heat treatment regimes for cast titanium armor.
Research into the influence of alloying elements (manganese, iron, and molybdenum) on the mechanical properties of titanium and titanium-aluminum alloys under dynamic and static loads was conducted under KD3-999-61. This study confirmed the significant influence of these additives under static loads and the absence of such an effect under dynamic loads (impact of an armor-piercing projectile). Furthermore, it was established that low-alloy alloys such as OT4-1 possess an optimal combination of mechanical properties. It was also demonstrated that the durability and survivability of commercially pure titanium, which is largely dependent on oxygen content, under certain conditions approaches the level of the OT4-1 alloy.
Development of plastic armored hulls
Work in this area was conducted during the TM-792-60 project. A full-scale model of the amphibious tank's hull was fabricated from fiberglass and tested using a firing test program according to the approved program. The tests confirmed the results obtained previously during firing of fiberglass plates. The experimental portion of this work is essentially complete.
In the fourth quarter, a detailed comparative analysis of the performance characteristics of fiberglass and steel armored hulls is planned, including weight, bullet resistance, radiation protection, detection by infrared and radar reconnaissance devices, etc.
Based on this analysis, it is proposed to outline the area of application of plastic armored hulls and determine their place in the general system of armored vehicles.
Development of welding and joining issues for armored vehicle parts
During the third quarter, work in this area received considerable attention due to the expansion of the range of materials used in modern tank construction and the great potential for introducing titanium and aluminum alloys into armor production.
Research on TM-854-60 focused on the kinetics of intermetallic phase formation reactions occurring during aluminum-titanium and aluminum-iron welding. Methods for automatic and manual aluminum-titanium welding were developed, yielding satisfactory weld seams (tested with 37mm caliber projectiles). Based on these methods, work is currently underway on welding a small armored hull mockup made from AMg6 and OT-4 alloys. Methods for producing bimetal from these alloys by jointly rolling plates have also been developed. A study of aluminum-iron weldability showed that brazing using zinc and cadmium solders yields the best results.
In the fourth quarter, it is planned to complete the work by checking and refining the obtained data and firing welded plates (aluminum-titanium).
On the topic TM-856-60, as a result of experimental work on welding titanium alloys with a thickness of 135-140 mm, a consistently obtained impact toughness of the welded seam equal to 4,5-4,8 kgm/cm was achieved2The quality of the flux (calcium fluoride) is crucial. Good results are achieved by adding up to 0,075% rhenium compounds to the flux, as well as by additionally shielding the weld pool with an argon jet. An attempt to use OT-4 alloy wire for welding was unsuccessful; VT-1 vacuum-treated titanium wire produces better results.
In the third quarter, 12 welded plates up to 140 mm thick were manufactured, including two plates intended for firing tests. Work is nearing completion on preparing the titanium alloy armor hull mockup for welding.
In TM-857-61, progress has been made in achieving high-quality butt welds on AMg250 alloy armor plates up to 6 mm thick. These joints are achieved by forming a multi-pass weld using a 4 mm diameter wire feed at a speed of approximately 600 m/hour. Considerable attention is also being paid to the study of welding conditions for aluminum sheets 20-40 mm thick. The relevance of this research is determined by the great potential of bulletproof aluminum armor.
Introduction of light alloys into the production of non-armored tank parts
During the implementation of projects TM-745-59 and HT2-328-61, a large number of experimental chassis components for various armored vehicles were manufactured and tested using lightweight titanium and aluminum alloys at several plants (STZ, UVZ, and UZTM), with the active participation of institute staff. In a number of cases, the testing demonstrated the full feasibility of using lightweight alloys to manufacture rocker arms, brackets, tensioning mechanisms, road wheels, and other components for several existing and planned tank systems. For example, the rocker arms and tensioning mechanisms of Projects 740 and 160, manufactured from VTZ-1 titanium alloy, demonstrated wear resistance comparable to that of production-standard components, as demonstrated by double the warranty period. Meanwhile, similar components installed on Projects 155 and 166 demonstrated increased wear under the same conditions. Currently, UVZ is completing the production of prototype fuel tanks, fighting compartment floors, spare parts boxes, and other components made from AMg6 aluminum alloy. Fourteen different hull and chassis components for Object 19 have been cast and machined from AL-14 alloy and have now been shipped to STZ for assembly. A number of components (six items) intended for the same purpose, made from wrought aluminum alloys, are currently in production.
As a result of this work, the range of parts for which it is entirely possible to use light alloys will be significantly expanded, which in some cases provides a quite noticeable weight gain (up to 600-1000 kg per vehicle).
LKZ is playing a limited role in this work. The experimental tracks made at this plant last year from VTZ-1 titanium alloy for Object 277 (an experimental 55-ton heavy tank) have not yet been tested, and experimental design work on introducing light alloys into tank construction is essentially just beginning for Object 287. The plant should be encouraged to pay closer attention to this pressing issue.
During the implementation of one of the stages of the NOZ-999-61 project, exploratory work was conducted to investigate the possibility of improving the mechanical properties of cast aluminum alloys intended for the manufacture of chassis components. Specifically, the effect of melt overheating using various refining and modifying fluxes was investigated. Eighty-three experimental melts were conducted, revealing the possibility of nearly doubling the ductility of the AL-83 alloy while simultaneously reducing its tensile strength by only 4-2 kg/mm.2Similar studies, so far without significant effect, are being conducted with AL-19 and AL7-4 alloys. Furthermore, work is underway to study the effect of minor additions of beryllium, lithium, titanium, and manganese on the properties of AM-9, AL7-4, and AL-4 alloys. Twenty-six test melts have been conducted.
To expand the application range of light alloys and improve the durability of non-armored structural tank components, research was conducted under Project TM-745-61 to improve the wear resistance of titanium alloys using chemical-thermal treatment methods. An optimal titanium alloy composition with good mechanical properties (tensile strength of 105 kg/mm) was selected.2 with an impact strength of 9,5 kgm/cm2), and heat treatment regimes were determined. It was proven that surface saturation of this alloy (to a depth of approximately 1 mm) with oxygen and carbon increases its wear resistance up to 100-fold under dry friction on both soft and hard steel, and by 2-4 times under abrasive action. The purity of case-hardened samples and their ductility are virtually unchanged.
Another section of this same topic (TM-745-61) provides for long-term corrosion testing, in both free and stressed states, of laboratory specimens from full-scale products made of various aluminum alloys to determine the effect of corrosion on their mechanical properties. Preliminary data (after 9 months of exposure to a corrosive environment) showed satisfactory resistance of AMG-6 and AMG-61, with no severe corrosion damage or noticeable reduction in mechanical properties.
For the TM-734-60 project, the design of the road wheels has been finalized, taking into account their manufacture from ML-5 magnesium alloy. These wheels and brackets were cast at Plant 219 and installed on Machine 119 at UZTM. Factory performance tests have now begun, the results of which allow us to evaluate the applicability of high-strength magnesium alloys in this application. Laboratory tests have been completed to determine the effect of shot peening on the wear resistance of magnesium alloys. The results are being processed.
Improving the tactical and technical properties of the torsion bar suspension of new medium and heavy tanks
Work in this direction is carried out on two topics: TM-736-60 and NOZ-999-61-3 (contractual with LKZ).
Topic TM-736-60. Based on the results of bench and road tests covering 3500 km, the design and manufacturing technology for torsion shafts designed for operation under torsion shaft stress during bench tests have been adjusted for the "432" prototype. No excessive shaft shrinkage or breakage was observed during road tests. Further testing of the prototype must be accelerated to obtain data on the shafts' performance at higher mileages before installing them on the "432" prototype. Simultaneously, a technology for manufacturing steel with even higher strength properties is being developed. Positive results obtained with flat specimens were not confirmed when testing round specimens due to the impossibility of their plastic deformation at the optimal process temperature of minus 55 degrees Celsius. Magnetic treatment of steel in fields up to 8 Gauss was tested. Further work in this section requires adjustments.
Topic HOZ-999-61. Bench tests were conducted at a stress of 10 kg/cm2 Seven-rod cluster shafts are being manufactured and undergoing performance testing at facility "272M." Three-rod cluster shafts for the same facility have been manufactured and rigged for testing, significantly simplifying the shaft manufacturing process and reducing the suspension weight by approximately 200 kg. Further performance testing of shafts 272-33-53 at LKZ must be expedited to incorporate their data into the design documentation. Joint work on shafts for facility "287," as stipulated by the contract, has been excluded from the plant's plan.
Development of materials and manufacturing technology for turbine parts of turbo-piston and gas-turbine engines
Work in this direction is carried out on two topics: TM-758-61 and NOZ-999-61-8.
Topic TM-758-61. For the 5TDF turbo piston engine, the 1961NBVA alloy was developed in the second quarter of 7, meeting the technical requirements: at 650° and a stress of 30 kg/mm2, with a failure time of at least 80 hours. The alloy's composition is currently being improved for use under higher operating conditions (720°-750° and stresses of 24 kg/mm). The properties of the 7NBVA alloy in the forged state are also being studied.
Work at the Malyshev Plant is carried out using this alloy in two applications: for both axial turbine blades and radial turbine impellers.
A technology for alloy smelting, casting, and heat treating blades has been developed under laboratory conditions. In the third quarter of the year, the plant, with the direct participation of the Branch, smelted seven heats, tested their properties, and mastered the smelting technology. Pilot batches of wheels and blades were cast, and centrifugal casting of impellers was mastered. Heat treatment of the wheels was carried out, during which cracks were detected. Adjustments were made to the pattern tooling. Measures to eliminate cracks in the impeller castings have been identified and are being experimentally tested. For standard heat treatment of parts, the Branch is transferring a G-7 furnace to the plant. Simultaneously, the Branch is refining the technology for casting and heat treating wheels from the 30NBVA alloy. Permission has been received from the organization "P.O. Box 7" to conduct pilot castings of these wheels. Work on the radial turbine is under extremely tight deadlines. The factory produced the moldings one month late, lacked heat treatment equipment, and inspection of the pilot castings was slow. Two sets of blades of the old design were cast from 126NBVA alloy, heat treated, and now automated welding is underway using a process developed in the laboratory.
Topic NOZ-999-61-7 is a research topic for testing refractory alloys for operation at a temperature of 1000 degrees Celsius for 400 hours at a stress of 25 kg/mm2, intended for gas turbine engine blades. Niobium-based alloys have been selected and smelted at PO Box 126 and the Institute of Metallurgy and Metallurgy of the USSR Academy of Sciences. Seven testing machines have been prepared, and tests of the RN-7 alloy in argon have been conducted. Testing of the VN-5A alloy with coatings to improve heat resistance has begun. For more extensive testing, the testing laboratory needs to be replenished with machines and specialized materials, as requested by the 2th Directorate.
Work to assist production
During the work on the TM-620-60 topic, a survey was conducted of the state of armor production technology, the quality of manufactured products and the degree of implementation of new technological processes at plants 78, UVZ, 174, ZhZTM, MMK, NTMK and KMK.
In order to eliminate the identified deficiencies, appropriate measures were developed in cooperation with the factories and a number of experimental works were planned, some of which have now already been completed.
At Plant 78, warping of the T-55 tank turrets during heat treatment was eliminated, and subsequent straightening under a press was eliminated.
At UVZ, with the aim of introducing low-nickel steel grades, pilot smelting of MBL-1 steel grade was carried out, and promising positive results were obtained.
At Plant 174, process instructions and drawings for the necessary equipment for hot-cutting risers have been prepared, and manufacturing of the tooling and stand has begun. Implementation of this technology will eliminate the need for high annealing, shorten the production cycle, and reduce fuel consumption. At the same time, the plant has updated existing technical documentation.
At ZhZTM, preliminary cooling of T-55 tank turrets before hardening was introduced into production, significantly reducing defects due to cracks, and exothermic heating of risers was introduced during casting of these turrets, which reduced steel consumption per unit of product by 700 kg.
At Magnitogorsk Iron and Steel Works (MMK), work is underway to improve the structure of the ingot heads through exothermic heating. Positive results have been achieved, and will be tested on a pilot batch in 1962.
Experiments are being conducted at NTMK to determine the feasibility of eliminating the slow cooling of sheets after rolling and direct hot-setting for tempering. Preliminary data have not yielded encouraging results, due to a significant increase in sheet warpage. A final conclusion will be reached after the completion of the entire research and testing program in October 1961.
Additionally, as a result of project TM-662-59, a process for mechanized rod production was developed and tested for Plant 73. The work has been completed and is being implemented into production.
On the TM-677-61 project, a series of experiments were conducted at the same plant to refine and fine-tune the sand-blowing machine's operating modes and the ramming of full-scale metal-shell molds. A pilot casting of the turret for Object 166 (T-62) was completed. Positive results were obtained. The work is ongoing.
At NTMK, heavy tank rims were smelted, rolled, heat-treated, and mechanically processed using a new steel grade containing reduced amounts of expensive alloying elements for the TM-715-60 project. Based on the running and firing tests of the manufactured rims, the feasibility of introducing the new steel grade into serial production was substantiated. The work is complete.
Research (subject phase NOZ-999-61) is investigating the possibility of increasing the cyclic strength of pearlitic cast steel intended for track link manufacturing. The effectiveness of isothermally treated 40ХС steel tempering is being tested, with application to cast track links. Simultaneously, 40СХ steel in the forged condition after isothermal treatment and tempering is being studied, with application to track links for the "432" product. The effectiveness of surface work hardening of 23ХГСЦ steel is being investigated, with application to cast LKZ track links.
Implementation of the work carried out by the Branch and the introduction of its results into practice
As part of the Institute's completed research project, as a separate phase of Project NOV-999-61, joint work was conducted with the K.B. and factories to enhance the protection of existing assets and implement radiation, cumulative, and combined protection methods developed by the Branch into the design and production of newly developed vehicles. The following work has been completed in this area to date:
- technical documentation was compiled, a prototype was manufactured, and production of a prototype of the T-55 tank began;
- technical documentation was compiled and a prototype of the T-10M tank was manufactured;
- one prototype of object 166 has been manufactured and the second prototype is being completed;
- all necessary documentation and materials (plastic plates) for the production of a prototype of object 432 with combined multilayer armor were sent to the plant;
- together with the Design Bureau of the LKZ, a radiation protection project for facility 287 was developed;
- the technical design has been reviewed and the Branch is participating in the development of technical documentation for the protection system for object 906 (an experimental light amphibious tank);
- Together with the design bureaus of ChTZ, ATZ and ZIL, a protection system for an infantry fighting vehicle (IFV) was developed and work on its technical design began.
In order to introduce radiation protection methods into serial production, it is necessary to file a petition to expedite the release of the relevant Resolution of the Council of Ministers of the USSR.
The document was signed by Vsevolod Vasilyevich Ierusalimsky, Deputy Director for Research at the VNII-100 Branch.
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